However, opponents of the EPA rules might not like the study's findings. The study says one reason costs will be higher is there are likely to be more polluted waterways in the state than the EPA had calculated, noting that "more than half of all waters could not be assessed due to insufficient data."

As a result, the agency failed to correctly figure in the number of lakes, streams, rivers, springs, bays and estuaries that would be classified as "impaired" by pollution, the study by the National Academy of Sciences found.

"The way they did it, they underestimated the number of waters that would be impaired," said Leonard Shabman, a Virginia water pollution expert who helped oversee the study.

The study also says opponents of the rules —- which includes many business leaders and most of the state's elected officials — have confused the EPA's estimates for the cost of enforcing the rules with the total cost of cleaning up all the pollution.

As for the cost to industry to stop the flow of pollution into waterways, "I don't know the cost — nobody knows the cost," Shabman, of the think tank Resources for the Future, said.

Ryan Banfill, a spokesman for the industry and agriculture groups opposing the EPA rules, hailed the study as "a confirmation of the chorus of concern." But Earthjustice attorney David Guest called higher costs "a fair price to pay to stop toxic green slime from breaking out on our waterways."

The EPA has postponed implementing the new rules until July because the state Department of Environmental Protection has come up with its own standards that may replace them.

In 1998, the EPA ordered all states to set numeric limits on nutrient pollution. Nutrients such as phosphorous and nitrogen flow into waterways from lawns, golf courses, leaking septic tanks and malfunctioning sewer plants, and feeds algae blooms that kill fish and cause respiratory problems and rashes among beachgoers.

Currently Florida has vaguely worded limits on nutrients that have failed to prevent some waterways from being heavily polluted.

The EPA warned the states that if they took no action by 2004, the agency would step in — but the EPA still didn't do anything. So in 2008 the Sierra Club and other groups sued the EPA.

The EPA settled the suit a year later by agreeing to set new limits. But business groups, agricultural leaders and politicians from both parties began complaining about the high cost, which has led to the EPA repeatedly delaying implementation.

The EPA estimated that its 168 pages of new standards could cost residents an extra 11 to 20 cents a day per household, or a total of $130 million to $200 million. The amount is based on industry and government costs that would be passed on to consumers. But opponents predicted it would be far higher — $21 billion.